Electrical pyrometer



June 14, 1938. s. RUBEN 2,120,374

ELECTRICAL PYROMETER Original Filed Oct. 25, 1931 Mievuroy deaf?? compound 11 j Z WAVE-25R BY ATTORNEY Patented June 14, 1938 UNITED STATES PATENT OFFICE ELECTRICAL rraomz'raa Application October 23, 1931. Serial No. 570,746 Renewed July 24, 1936 2 Claims.

This invention relates to electrical pyrometers and heat indicating systems. Specifically, it relates to a device utilizing the resistance change 'of a metallic compound under the influence oi wise, for instance as a relay to directly control.

such instruments as valves or switches.

A further object of the invention is to provide .a device for measuring the temperature of an internal combustion engine and attachable either to the outside or through the engine casing without interfering with any of the parts thereof.

Another object of the invention is to provide an electrical device for measuring the temperature of the engine of an automobile.

Other objects of the invention and objects re- 20 and assembling the various parts of the apparatus and the electrical connections therefor will be apparent as the description of the invention proceeds.

The characteristic property of the material employed for the temperature indicating resistance element is one having a high negative resistance coemcient. In the art, many compounds having this property have been applied for purposes and objects similar to those of applicants, but they have been subject to certain inherent limitations and infirmities such as variations from initially fixed values, failing to accurately repeat resistance values with changes in temperature, chemical instability and crystal structure changes with temperature variations, electrolytic decomposition, etc. In addition, it has been dimcult to reproduce units within close limits.

My invention consists in utilizing as the electrical resistance material, an oxide of vanadium such as vanadium pentoxide, to overcome the above limitations. When fused and cast, I have found this material to be stable and accurately 45 responsive to temperature variations, returning always to its initial resistance value. When employed in combination with a source of potential and a meter having an electrically balanced movement to compensate for voltage supply 50 variations, it affords a thoroughly reliable temperature indicating means.

While this application describes and the drawing illustrates the use of the temperature responsive element chiefly in association with heat pro- 55 ducing machines, such as internal combustion lating particularly to the method of constructing engines, the device is likewise practicable in association with cold producing machines, such as industrial and home type refrigerators.

In order to illustrate the invention, reference is made to the accompanying drawing, in which is shown a device for measuring the temperature in an internal combustion engine, such as an automobile motor.

Flg. 1 is a sectional view of the temperature responsive element and its housing.

Fig. 2 is a view showing the device locked into the top of a motor casing and in series with a meter and battery.

Fig. 3 is a graph showing the temperature resistance characteristics of the resistance element.

Referring more specifically to the drawing, in Fig. l the brass shell I houses at the lower end a. porcelain plug 2 which partly supports and centers brass electrode rod 3 which extends into the head of and is further held in place and contacted by brass screw 9; the solidified mass of fused vanadiumpentoxide 4 has been melted and poured into the brass electrode shell I and around electrode rod 3, the shell I having a threaded end 5 to enable the unit to be screwed into the motor casing; the resistance material 4 is protected by waterproof sealing compound II; insulator" top I is held in place by nut l and lock nut 6 which latter also serves to hold the entire device in place. In order to prevent surface oxidation, the contacting portion of the inner wall of shell electrode 1 may be lined with graphite l6; chromium plating is likewise effective for this purpose. If the shell is composed of metals not easily oxidized, however, this procedure 'is unnecessary.

In Fig. 2, the device is shown screwed into motor easing H adjacent the water jacket, the motor casing serving as a contact through lock nut 6; the meter i2 has an electrically balanced movement to compensate for voltage changes in the supply circuit, this being accomplished through the use of coils l3 and I4 shown in phantom; voltage is supplied from battery IS the positive terminal of which is connected to coil IS, the negative side being connected to coil l4 and the casing of the motor II; the circuit is completed through connection of the resistance device to the meter l2 through nut 8.

In the graph shown in Fig. 3, R represents the 50 resistance and T the temperature.

In operation of the device as connected in Fig. 2, at ordinary cool temperature, with the engine and the vanadium pent-oxide cold, the device will pass little or no current from the battery. When 55 the temperature of the engine begins to rise, however, the resistance of the vanadium pentoxide decreases, more current flows and the temperature is thereby relatively indicated on the meter.

I claim:

1. An electrical temperature indicating device comprising a tubular metal shell having an electrically conducting-lining of a material difllshell and intimately contacting said lining, and a cooperating electrode contacting said vanadium pentoxide and suitably insulated from the shell electrode, the length of said pentoxide mass exceeding the inner diameter or said shell.

2. In an electrical temperature indicating device including a tubular metal shell having an electrically conducting lining of a material difllcult to oxidize on its inner contacting surface and constituting one electrode, and a second electrode insulated from the shell electrode, a

- SAMUEL RUBEN. 

